1. Field of the Invention
The present invention relates to a heat sink for cooling a semiconductor element which emits much heat such as a micro processing unit (referred to as an MPU hereinafter).
2. Description of the Prior Art
Heat sinks have been used for cooling semiconductors and the like which emit much heat. Recently, in particular, a fan-motor-integrated heat sink incorporated with a small fan is used for coping with the high heat emission of the MPU etc.
Conventional heat sinks will be described hereinafter. FIG. 8 is a perspective view of a conventional heat sink and FIG. 9 is a cross sectional view of the conventional heat sink.
In FIGS. 8 and 9, reference numeral 81 denotes an MPU that is a high-exothermic semiconductor element, 82 a heat sink substrate which is mounted on the MPU 81, 83 radiator fins, 84 driving means such as a motor or the like, 85 a fan and 86 a structure such as the casing of a notebook-type personal computer etc. for defining a space above the heat sink.
The operation of a conventional fan-motor-integrated heat sink having the aforementioned structure will be described hereinafter. Heat emitted from the MPU 81 is transmitted to the heat sink substrate 82 and the radiator fins 83. Air flow generated by the fan 85 rotated by the driving means 84 is taken in between the structure and the upper surface of the heat sink as shown by an arrow A and passes among the radiator fins 83 while carrying off heat therefrom to be vented from the side surface thereof as shown by an arrow B.
The aforementioned conventional structure had a problem that it was impossible for thin devices such as the notebook-type personal computer limited in thickness to secure a sufficient space for taking in air from above the heat sink and consequently to secure a sufficient cooling performance. Although the entire heat sink may be made thin for securing sufficient space, a motor capable of rotating the fan to generate a sufficient amount of air flow for cooling the device required a certain degree of thickness because of the structure of its bearing and coil, so that the motor was structurally limited in being made thin.